728 TRANSACTIONS OP SECTION K. 



surrounded by roots and petiolar bases, rather suggesting a habit similar to that 

 of Todea harhara. 



The lower face of the fossil was of an irregular elliptical shape 7 cms. long 

 by 4*3 cms. wide. Each stele on this face showed three or four petioles. 



The upper face, which was much larger, 7 cms. by 8 cms., had been fractured 

 obliquely, so that the greatest length of the specimens on one side was approxi- 

 mately 8 cms., while on the other side it was only 3 cms. In this length of stem 

 each stele gave rise to two leaf-traces, so that the departure of six leaf-traces 

 can be seen in the whole block. 



The sections which have been cut show excellent preservation of the tissues. 

 Both stems and leaves bear external glands or hairs. The stem stele is of a 

 five-rayed star-shape with blunt points, the pith, which contains tracheids, being 

 also star-shaped. The structure is in the main of the Ankyropteris Grayi typo 

 with less acute pointS; but with no axillary branches. Leaf-traces leave the 

 stele in the same order and manner as described for A. Grayi. As each departs 

 it is of a triangular shape with rounded angles, the apex of the triangle being 

 the point of attachment to the stem. This bundle soon becomes flattened 

 tangentially, so that before it leaves the cortex it has the appearance of a 

 flattened ring, slightly curved, with the convexity of the curve on the adaxial 

 side. As the trace passes outwards it becomes still more flattened and tan- 

 gentially elongate, until when a little above the base of the petiole it appears 

 as a long band-shaped xylem mass, without curvature, rather constricted in the 

 middle, and with a peripheral loop containing parenchyma and small tracheids at 

 each end. Thus the petiolar structure is of the Clepsydropsoid type. None of 

 the petioles are continued high enough to show detached pinna traces, though 

 they are high enough to show that the simple type of petiole structure is main- 

 tained and it does not pass into a more complicated state, as in Diplolabis and 

 Ankyropteris. Preparations for the departure of pinna traces are seen in some 

 petioles. The traces, which are in two series, one from each peripheral loop, 

 consist of a ring of tracheids with parenchyma in the centre, very like those 

 figured for Clepsydropsis antiqua. 



The combination of the outstanding features of this fossil — the A. Grnyi 

 type of stele, the absence of axillary branches, and the simple Clepsydropsoid 

 petiole — defines it clearly as a new type and an interesting addition to the 

 already known members of the Zygopterideee. 



6. Tlic Formation of Auximones from. Nitrogenous Organic Suhstances. 

 By Professor W. B. Bottomlet, M.A. 



The bacterial scum formed on crude nitrifying culture solutions in the 

 presence of auximones has provided a method for investigating the occurrence 

 of these substances. 



It has been found that auximones are formed during the germination of 

 seeds, and enable the young embryo to utilise the food material present in the 

 seed. The phosphotungstic fraction from dry wheat, pea and maize seeds gave 

 no scum. A similar fraction from seeds which had germinated for two days 

 yielded a thick scum. Excised young embryos of wheat and maize failed to 

 grow in Detmer's culture solution, but flourished in culture solution containing 

 one part in three millions of auximone. 



Auximones are formed during the humification of nitrogenous organic 

 matter, and the amount of auximone present depends on the extent of humifica- 

 tion. Fresh stable manure, two-year-old rotted manure, and bacterised peat 

 were fractionised in the usual manner. The minimum quantity of these frac- 

 tions necessary to produce a scum were as follows : 



Fresh manure extract from 50 grms. 



Rotted manure ,, „ 10 grms. 



Bacterised peat „ ,, 0*2 grms. 



The relative proportion of auximone is therefore 1:5: 250. Hence the amount 

 of auximones increases with the progressive humification of the organic matter. 



